| 1 | //go:build linux |
| 2 | |
| 3 | package host |
| 4 | |
| 5 | import ( |
| 6 | "os" |
| 7 | "path/filepath" |
| 8 | "syscall" |
| 9 | "time" |
| 10 | "unsafe" |
| 11 | |
| 12 | "github.com/carlosframework/platform/internal/moves" |
| 13 | ) |
| 14 | |
| 15 | // measureDiskSize is how much T11's disk measurement writes and reads back. |
| 16 | const measureDiskSize = 64 << 20 |
| 17 | |
| 18 | // measureDiskRate times writing and reading measureDiskSize under dir with |
| 19 | // O_DIRECT, so the page cache neither absorbs the write nor answers the |
| 20 | // read (F12). A filesystem that refuses O_DIRECT (tmpfs) is measured with a |
| 21 | // plain write, fsync and read instead. |
| 22 | func measureDiskRate(dir string, now func() time.Time) (moves.MeasuredRate, error) { |
| 23 | path := filepath.Join(dir, "disk") |
| 24 | f, err := os.OpenFile(path, os.O_CREATE|os.O_EXCL|os.O_RDWR|syscall.O_DIRECT, 0o600) |
| 25 | if err != nil { |
| 26 | return measureDiskSynced(dir, now) |
| 27 | } |
| 28 | defer f.Close() |
| 29 | buf := alignedBlock(1 << 20) |
| 30 | start := now() |
| 31 | for n := 0; n < measureDiskSize; n += len(buf) { |
| 32 | if _, err := f.Write(buf); err != nil { |
| 33 | return moves.MeasuredRate{}, err |
| 34 | } |
| 35 | } |
| 36 | if err := f.Sync(); err != nil { |
| 37 | return moves.MeasuredRate{}, err |
| 38 | } |
| 39 | if _, err := f.Seek(0, 0); err != nil { |
| 40 | return moves.MeasuredRate{}, err |
| 41 | } |
| 42 | for n := 0; n < measureDiskSize; n += len(buf) { |
| 43 | if _, err := f.Read(buf); err != nil { |
| 44 | return moves.MeasuredRate{}, err |
| 45 | } |
| 46 | } |
| 47 | return moves.RateOf(2*measureDiskSize, now().Sub(start), now().UTC()), nil |
| 48 | } |
| 49 | |
| 50 | // alignedBlock is a size-byte buffer aligned to 4096 bytes, as O_DIRECT |
| 51 | // requires. |
| 52 | func alignedBlock(size int) []byte { |
| 53 | const align = 4096 |
| 54 | b := make([]byte, size+align) |
| 55 | off := 0 |
| 56 | if r := int(uintptr(unsafe.Pointer(&b[0])) & (align - 1)); r != 0 { |
| 57 | off = align - r |
| 58 | } |
| 59 | return b[off : off+size] |
| 60 | } |
| 61 | |
amadan